Nematic liquid crystalline compositions having extended mesomorphic range

ABSTRACT

Compositions formed from nematic liquid crystalline compounds are disclosed. The novel compositions of the invention have extended nematic mesomorphic temperature ranges which are significantly larger than those of the individual components of the compositions and are stable at relatively low temperatures.

8o cats-$188113 United States Haas et a1.

[ NEMATIC LIQUID CRYSTALLINE COMPOSITIONS HAVING EXTENDED MESOMORPI-IICRANGE [75] Inventors: Werner E. L. Haas; John B.

Flannery, In, both of Webster; Bela Mechlowitz, Rochester; James E.Adams, East Ontario, all of NY.

[73] Assignee: Xerox Corporation, Stamford,

[51] Int. Cl 603g 13/10, 603g 9/04, 0021' 1/28, G02f1/36, G03b 21/24,350 160 LC 1 June 11, 1974 3,689,525 9/1972 Scheurle ct a1. 260/273 RFOREIGN PATENTS OR APPLICATIONS 1,170,486 11/1969 Great Britain 252/408OTHER PUBLICATIONS Liquid Crystals Draw Intense Interest, Chemical andEngineering News, Nov. 1, 1971, pp. 20-23.

Kelker et al., A Liquid-Crystalline (Nematic) Phase with a ParticularlyLow solidification Point, Angew. Chem. Internat. Edit, Vol. 8, No. 11,pp. 884-885 (1969).

Primary ExaminerNorman G. Torchin Assistant Examiner.1. P. BrammerAttorney, Agent, or FirmJames .1. Ralabate; David C. Petre; Gaetano D.Maccarone [57] ABSTRACT 1 58 Field of Search 96/1; 252/408; 353/84Compositions formed from nomatio liquid Crystalline compounds aredisclosed. The novel compositions of [56 References Ci the inventionhave extended nematic mesomorphic UNITED STATES PATENTS temperatureranges which are significantly larger than 3 597 044 8/1971 C t H350/160 LC those of the individual components of the composias e ano362559' W97! Freiser t I I 350/160 LC trons and are stable at relativelylow temperatures. 3,627,408 8/1971 Ferguson 353/84 11 Claims, 11 DrawingFigures 3 5 1, 5,1 3 .j 0am os/ta 1 7 s t alalellls MENTH'JJIII: 1 I mSHEEI t UP 5 ABUTA HEXOBUTA ISOTROPIC NEMATIC SOLID FIG. 7

NEMATIC LIQUID CRYSTALLINE COMPOSITIONS HAVING EXTENDED MESOMORPIIICRANGE BACKGROUND OF THE INVENTION This application relates generally toliquid crystalline compositions. More particularly the invention relatesto such compositions having extended nematic mesomorphic temperatureranges which are stable at relatively low temperatures and their use inelectro-optic applications.

Liquid crystalline substances exhibit physical characteristics some ofwhich are typically associated with liquids and others which aretypically unique to solid crystals. The name liquid crystals" has becomegeneric to substances exhibiting these dual properties. Liquid crystalsare known to appear in three different forms: the smectic, nematic andcholesteric. These structural forms are sometimes referred to asmesophases thereby indicating that they are states of matterintermediate between the liquid and crystalline states. The threemesophase forms of liquid crystals mentioned above are characterized bydifferent physical structures wherein the molecules of the compound arearranged in a structure which is unique to each of the three mesomorphic structures. Each of these structures is well known in theliquid crystal art.

In the smectic structure the molecules are arranged in layers with theirmajor axes approximately parallel to each other and approximately normalto the planes of the layers. Within a given layer the molecules may beorganized in uniform rows, or randomly distributed throughout the layer,but in either case the major axes are still approximately normal to theplane of the layer. The attractive forces between layers are relativelyweak so that layers are free to move in relation to each other therebyproviding the smectic liquid crystalline substance with the mechanicalproperties of a planar or two-dimensional, soap-like fluid.

In the nematic structure the major axes of the molecules lieapproximately parallel to each other but the molecules are not organizedinto definite layers as is the case in the smectic structure.

The sensitivity of the optical properties of nematic liquid crystals toelectric fields makes these materials extremely useful forelectro-optical applications. For example, dynamic scattering is commonto many materials which exhibit nematic liquid crystalline mesophases.The so-called dynamic scattering state occurs when an ionic current flowis set up through the nematic liquid crystalline material and thenematogenic material assumes a non-selective light-scatteringappearance. This phenomenon may be utilized in electro-optical .devices'such as, for example, display systems.

Heretofore a serious drawback with respect to potential uses ofnematogenic materials in electro-optic devices has been the relativelyhigh temperatures at which the majority of the known nematic materialsbecome mesomorphic. Typically, electro-optic devices are operated at ornear room temperature. Thus devices utilizing such nematic liquidcrystalline materials would require additional apparatus to maintain thetemperature of the liquid crystalline material within its mesomorphicrange thereby undesirably complicating the overall device configuration.

Recently there was disclosed in the art a nematogenic material which isliquid crystalline at room temperature. H. Kelker and B. Scheurle, inAngew. Che., Inter. Ed. 8, 884 (1969), reported the preparation ofpmethoxybenzylidene-p-n-butylaniline (ABUTA) which has the chemicalformula:

where R CH and R C I-I and has a nematic mesomorphic range of from about20C to about 41C. While this compound has been found to be very usefulin various electro-optic techniques nevertheless there exists acontinuing need for liquid crystalline materials which have a nematicmesophase at or near room temperature.

SUMMARY OF THE INVENTION It is, therefore, an object of this inventionto provide liquid crystalline materials having the above-describeddesirable features.

It is another object of the invention to provide novel liquidcrystalline compositions.

It is a further object of the invention to provide liquid crystallinecompositions having nematic mesomorphic temperature ranges which aresignificantly larger than those of the individual components thereof.

It is a still further object of the invention to provide liquidcrystalline compositions which have a nematic mesophase at or near roomtemperature.

Yet another object of the invention is to provide such liquidcrystalline compositions which are useful in electro-opticalapplications.

A still further object of the invention is to provide such liquidcrystalline compositions which may be utilized in electro-optic displaydevices.

These and other objects and advantages of the invention are accomplishedby providing novel liquid crystalline compositions which are formed bymixing together liquid crystalline compounds having a general formulaand which have a nematic mesophase which is stable at relatively lowtemperatures.

Liquid crystalline compounds which belong to the class of compoundshaving the general formula and wherein R, and R are particularcombinations of alkyl groups are disclosed in copending application Ser.No. 179,732, filed Sept. 13, 1971 now abandoned, on the same day as thepresent application and hereby incorporated by reference herein. Thecompounds disclosed in the copending application are listed in Table Ibelow:

TABLE I Bmeetle Nematlc R1 R2 0.) C.) Name C H1 CIHQ 39-59 pn-PropoxybenZylidene-p-nbutylaniline.

CIH'... (34H, 7-46 46-75 p-n-Butox benZyIidene-pmbutylaniline.

CaHn.-. 04H 24-54 54-71 p-qz-Pentyloxybenzyljdene-pn-butylaniline.

C.Hi;. ClHO 25-70 70-78 p-n-HexyloxybenZylidene-pnylani a M W..-

C1H 04H, 29-76 7677.5 p-n-T-IeptyloxybenzyIidene-pn-butylaniline.

C411,. CH; (49)-66 66-63 pm-Butoxybenzylidene-ptoluidine.

CH CzH5 42-52 52-67 p-rr-Butoxybenzyhdene-pethylaniline.

CBHIL-.. CH3 35-45 45-64 pm-Pentyloxybenzylidene-ptoluidine.

Denotes monotropic transition.

[(6552: seen that the novel compounds disclosed in the copendingapplication each possess a nematic mesophase which is stable atrelatively low temperatures, i.e., near room temperature. Thesecompounds have been found to be highly advantageous for use in variouselectro-optic applications such as, for example, display devices.

Now it has been surprisingly found that by utilizing some of thecompounds listed in Table l and otherv PENTOBUTA) and ABUTA; andmixtures of p-nhexyloxybenzylidene-p'-n-butylaniline (hereafterHEXOBUTA) and ABUTA. As will be seen below an extremely importantcharacteristic of these novel compositions is that they typically havenematic mesophases which are stable at room temperature or slightlybelow and in some cases significantly below typically extending to below0C.

Thus it will be recognized that the compositions of the invention arehighly advantageous when employed in various electro-optic applicationssince they allow overall device considerations to be desirablysimplified. The novel compositions of the invention may be convenientlyutilized in any number of electro-optic applications such as forexample, display cells since upon application of an electric field ofsufficient magnitude, e.g., above about 3,000 volts/cm, the opticalproperties of the materials change and the liquid crystal material whichis substantially transparent prior to the application of the fieldbecomes frosted, i.e., exhibits dynamic scattering. For a detaileddescription of this phenomenon see G. H. Heilmeier et al., Proc. IEEE56, 7 (1968).

The foregoing and other objects and advantages of the invention will bemore readily understood from the following detailed description ofpreferred embodiments thereon particularly when viewed in conjunctionwith the accompanying drawings wherein:

FIG. 1 through FIG. 7 are graphical plots illustrating the eutecticbehavior of the respective compositions of the invention with respect tovarying mol fractions of the individual components thereof;

FIG. 8 is a partially schematic cross-sectional view of a liquidcrystalline imaging member;

FIG. 9 is a partially schematic isometric view of an embodiment of aliquid crystalline imaging member wherein the desired image is definedby the shape of at least one of the electrodes;

FIG. 10 is a partially schematic isometric view of an embodiment of aliquid crystalline display device; and

FIG. 11 is a partially schematic cross-sectional view of an embodimentof a liquid crystalline imaging member wherein at least one of theelectrodes has a photoconductive surface.

Generally speaking the individual compounds used to form thecompositions of the invention are prepared by condensation in refluxingethanol of the respective p-nalkoxybenzaldehyde and the appropriatep-nalkylaniline. Refluxing is carried for several hours and the solventis then removed by distillation. The crystalline products are thenpurified by repeated recrystallization from an appropriate solvent suchas methanol or petroleum ether. For a detailed description of theprocedures used in forming these compounds see the copending applicationreferred to earlier. The compositions are prepared by weighingappropriate fractions of the desired constituents, combining them in avessel, e.g., a glass beaker, and heating above'the isotropic transitiontemperatures of the respective constituents with mixing to ensure ahomogeneous composition.

The temperatures at which transitions from the nematic mesomorphic stateto the isotropic state occur, as indicated in FIGS. 1 through 7 for therespective compositions, are determined by differential thermal analysisemploying a DuPont 900 Differential Thermal Analyzer equipped withchrome] alumel thermocouples. The therrnograms are obtained at a heatingrate of 10C/minute and the temperature at the beginning of the statetransition endotherm is taken as the characteristic temperature. Thetemperature is determined by linear extrapolation of the leading edge ofthe endotherm to its intersection with the baseline.

Verification of the state assignments is obtained by polarized opticalmiscoscopy. Samples of these compositions are placed in the form of thinfilms, between glass cover slides and viewed through a Leitz Ortholuxpolarizing microscope having a calibrated hotstage. Visually observedtexture changes have been found to coincide within 2C with the phasetransitions observed y. thermal na ys Referring now to FIG. 1 there isseen a graphical plot illustrating the eutectic behavior of compositionsprepared from varying mol fractions of BOBUTA and ABUTA. The nematicmesomorphic temperature range for BOBUTA is from about 46C to about Cand that for ABUTA from about 20C to about 41C. It can be seen that thecompositions possess extended nematic mesomorphic temperature rangeswhich generally increase progressively as the weight percent of theBOBUTA increases and which reach a maximum at frorn about S Sto about 65weight percent BOBUTA.

FIG. 2 illustrates the eutectic behavior of compositions prepared fromvarying weight percentages of EOBUTA and ABUTA. The nematic mesomorphictemperature range for EOBUTA is from about 38C to about 82C. Thecompositions possess extended nematic mesomorphic temperature rangeswhich reach a maximum at from about 50 to about 70 weight percent ofABUTA.

FIG. 3 illustrates the eutectic behavior of compositions prepared fromvarying weight percentages of BOBUTA and EOBUTA. The compositions areseen to have extended nematic mesomorphic temperature ranges which reacha maximum at from about 55 to about 75 weight percent of EOBUTA.

The eutectic behavior of compositions prepared from varying weightpercentages of BOETHA and ABUTA is shown in FIG. 4. BOETHA has a nematicmesomorphic range of from about 48C to about 625C. The compositions haveextended nematic mesomorphic temperature ranges which generally increaserapidly as the proportion of the ABUTA constituent increases and whichreach a maximum at from about 60 to about 80 weight percent of ABUTA.

FIG. 5 illustrates the eutectic behavior of compositions prepared fromvarying weight percentages of B0- ETHA and EOBUTA. The compositions haveextended nematic mesomorphic temperature ranges which reach a maximum atfrom about 70 to about 90 weight percent EOBUTA.

FIG. 6 graphically illustrates the eutectic behavior of compositionsprepared from varying weight percentages of PENTOBUTA and ABUTA.PENTOBUTA has a nematic mesomorphic temperature range of from about 54to about 71C. The compositions have extended mesomorphic temperatureranges which generally increase rapidly as the proportion of the ABUTAconstituent increases and which reach a maximum at from about 50 toabout 80 weight percent of ABUTA.

The eutectic behavior of compositions prepared with varying molfractions of HEXOBUTA and ABUTA is illustrated in FIG. 7. HEXOBUTA has anematic mesomorphic temperature range of from about 70 to about 78C. Thecompositions are seen to have extended nematic mesomorphic temperatureranges which generally become larger as the proportion of the ABUTAconstituent increases and which reach a maximum at from about 50 toabout 70 weight percent of ABUTA.

As was discussed previously the novel compositions of the invention maybe utilized in a variety of electrooptic devices and provide simplifiedapparatus considerations therefore because of their stability at roomtemperature or below. I

FIG. 8 illustrates a typical liquid crystalline electrooptic cell inwhich the novel compounds of the invention may be utilized. Referringnow to FIG. 8 there is seen a liquid crystalline electro-optic cell 10,sometimes referredto as an electroded imaging sandwich, which is shownin partially schematic cross-section and wherein a pair of plates,generally designated 12, comprise a parallel pair of electrodes at leastone of which is substantially transparent. An electro-optic cell whereinboth electrodes are transparent is preferred when the cell is to beviewed using transmitted light; however a liquid crystallineelectro-optic cell may also be viewed using reflected light therebyrequiring only a single transparent electrode while the other is opaque.For purposes of illustration both electrodes 12 are shown as beingsubstantially transparent and are comprised of, in this illustrativeinstance, a substantially transparent conductive layer 13 upon thecontact surface deposited on a transparent support member 14. A typicalsuitable electrode for use in electro-optic cell 110 is commerciallyavailable under the name NESA glass from Pittsburgh Plate Glass Companyand is made up of a thin transparent electrically conductive layer oftin oxide overlying a transparent glass substrate.

The transparent electrodes 12 are separated by spacing member 16 whichcontains voids which form one or more shallow cups which contain theliquid crystalline film or layer 117 which comprises the active elementof the electro-optic cell. Liquid crystalline film 17 may be comprisedof any of the novel liquid crystalline compounds of the invention ormixtures thereof. A field is created between the electrodes by means ofan external circuit, generally designated 18 which typically comprises asource of potential 20 which is connected across the two electrodesthrough leads 22. The circuit 118 may also contain suitable switchingmeans. The potential source 20 may be either D.C., A.C., or acombination thereof.

When an electric field of sufficient magnitude, e.g. above about 3,000volts/cm, is applied across the liquid crystalline film the opticalproperties of the liquid crystalline material change and the liquidcrystal film, which is substantially transparent prior to theapplication of the field, becomes frosted, i.e., exhibits dynamicscattering. Thus the electro-optic cell can function as a light shuttersince a large percentage (e.g. about percent of incident light would bescattered and removed from the incident light while only a smallpercentage, e.g., about 10 percent would be transmitted.

In the liquid crystalline electro-optic cell described in FIG. 8 theelectrodes may be of any suitable transparent conductive material.Typical suitable transparent, conductive electrodes include glass orplastic substrates having substantially transparent and continuousconductive coatings of conductors such as tin, indium oxide, aluminum,chromium, tin oxide or any other suitable conductor. These substantiallytransparent conductive coatings are typically evaporated onto the moreinsulating transparent substrate. Where an opaque electrode is employedin the electro-optic cell any suitable electrode material may be used.In FIG. 8 the spacer 16, which separates the transparent electrodes andcontains the liquid crystal film 17 between the electrodes is typicallychemically inert, transparent, substantially insulating and hasappropriate dielectric characteristics.

Materials which are suitable for use as typical insulating spacersinclude cellulose acetate, cellulose triacetate, cellulose acetatebutyrate, polyurethane elastomers, polyethylene, polypropylene,polyesters, polystyrene, polycarbonates, polyvinylfluoride,polytetrafluoroethylene, polyethylene terephthalate, and mixturesthereof. These spacers, which also approximately define the thickness ofthe imaging layer or film 17 of liquid crystalline material, arepreferably of a thickness in the range of about ll) mils or less.Optimum results are typically attained with spacers in the thicknessrange between about A mil and about 5 mils.

FIG. 9 describes a liquid crystalline electro-optic imaging cell. Inthis preferred embodiment the desired image is defined by the shape ofan electrode and, therefore, by the shape of the corresponding electricconfiguration; however it will be understood by those 10 skilled in theart that both electrodes could easily be made in a matched pair todefine the same desired image. When the single image electrodeconfiguration is used the second electrode will comprise transparentsubstrate 14 with substantially transparent conductive 15 coating 13upon the entire area of the inner surface of the transparent electrode.It is noted that a very thin, or substantially invisible conductor 28 istypically used in this embodiment to electrically connect the electrodein the desired image configuration to an external circuit which issimilarly connected to the conductive coating of the opposite electrode.In operation this embodiment will produce an electric field only inareas where there are parallel electrodes, i.e., between the electrodein the desired image configuration and the opposite electrode, whetheror not the second electrode is also in the desired image configuration.Again here, one of the electrodes may be opaque if it is desired toobserve the imaged cell by reflected light rather than transmittedlight.

Additionally, where the desired image is defined by the shape of one ormore electrodes, an electrode may be shaped in the configuration of thebackground of the desired image and an imagewise electrode and such acorresponding background electrode may be coplanar 5 and insulated fromone another by an open space or insulating material. Such a coplanarpair of electrodes may be operated simultaneously as a substantiallyfullarea electrode.

FIG. 10 describes a preferred embodiment of a liquid crystalline imagingcell embodying an x-y grid and comprising two transparent planarsubstrates 32 and 34 which are parallel. On the inner surface 36 ofsubstrate 32 are arranged an array of transparent conductive strips allrunning in one direction. Four strips or electrodes, designated 38a,38b, 38c, 38d, and which have parallel longitudinal axes are shown;however it will be understood that in actual practice a much largernumber of electrodes may be used. On the inner surface 40 of substrate34 are arranged an array of transparent conductive electrodes 42a, 42b,42c, 42d having parallel longitudinal axes and being positionedsubstantially perpendicularly to the direction of the conductive strips38a-38d on substrate 32. Again it will be understood that in actualpractice a much larger number of electrodes may be arranged on innersurface 40 of substrate 34. The space between substrates 32 and 34 isfilled with liquid crystalline which can be any of the novel compoundsof the invention or mixtures thereof.

It will be understood by those skilled in the art that when twoelectrode strips, each being perpendicular to the other, are energizedwith an applied voltage, the portion of the liquid crystal cellcorresponding to the intersection of the two electrodes which have beenenergized will become darker than the remaining area of the cell. Byenergizing more than one electrode strip from each set, a plurality ofpredetermined areas are made to appear darker.

FIG. ll describes still another preferred embodiment of a liquidcrystalline electro-optic imaging cell wherein one of the electrodescomprises a photoconductor and imaging is effected by applying a uniformpotential across the entire area of the electrodes and subsequentlyexposing the photoconductor to an imagewise pattern of activatingelectromagnetic radiation corresponding to a desired imageconfiguration. Referring now to FIG. ll there is seen an electro-opticimaging cell, generally designated 50, wherein a pair of plates,generally designated 52 and 54 respectively, comprise a parallel pair ofelectrodes at least one of which is substantially transparent. Forpurposes of illustration both electrodes are shown as being transparent.Electrode 52 is made up of a photoconductive insulating material layer53 overlying a conductive substrate which in this instance is shown as asubstantially transparent conductive layer 51 deposited on asubstantially transparent support member 55. Electrode 54 is shown as asubstantially transparent conductive layer 56 deposited on substantiallytransparent substrate 57.

When it is desired to view the electro-optic cell using transmittedlight it is preferred that both electrodes be substantially transparent.Of course in this instance there is required a photoconductiveinsulating material layer which is substantially transparent to theactivating electromagnetic radiation. Typical suitable substan tiallytransparent photo-conductive materials include, for example, relativelythin, e.g., about 5 microns, layers of selenium. However theelectro-optic imaging cell may also be viewed using reflected lightthereby requiring only a single transparent electrode while the othermay be opaque. In this instance one of the electrodes is preferably madeup of an opaque photoconductive insulating layer deposited on an opaquesubstrate which may be any suitable conducting material such as ametallic layer.

The transparent electrodes are separated by spacing member 16 whichcontains voids which form one or more shallow cups which contain theliquid crystalline film or layer ll7. The electrodes are connected toopposite terminals of an external circuit 18. When a potential isapplied to the conducting surface 51 of electrode 52 in the dark nocurrent will flow and no field will be established across the liquidcrystal film since layer 53 is insulating under these conditions.However when the imaging cell is exposed to an imagewise pattern ofactivating radiation, the light-struck areas of photoconductiveinsulating layer 53 become conductive causing current to flow andestablishing a field across the liquid crystal film in the light-struckareas. The electric field causes the optical properties of the liquidcrystalline material to change and the liquid crystal film, which issubstantially transparent prior to the application of the field, becomesfrosted, i.e., exhibits dynamic scattering thereby effecting imaging.When the imaging cell is viewed by reflected light the image willtypically appear as milky-white image areas on a dark background. Whenthe imaging cell is viewed using transmitted light the image willtypically appear as dark image areas with transparent non-image orbackground areas.

Although the invention has be en described in detail with respect tovarious preferred embodiments thereof it is not intented to be limitedthereto but rather it will be recognized by those skilled in the artthat modifications and variations are possible which are within thespirit of the invention and the scope of the claims.

What is claimed is: 1. Liquid crystalline compositions comprising fromabout 55 to about 65 weight percent of and from about 35 to about 45weight percent of 2. Liquid crystalline compositions comprising about 50to about 70 weight percent of and about 30 to about 50 weight percent of7' Q 3. Liquid crystalline compositions comprising about 60 to about 80weight percent of and from about 20 to about weight percent of 4. Liquidcrystalline compositions comprising from about to about 80 weightpercent of and from about 20 to about 50 weight percent of 5. Liquidcrystalline compositions comprising from about 50 to about 70 weightpercent of and from about 30 to about 50 weight percent of applying anelectric field across said liquid crystalline material, said electricfield being of sufficient strength to transform said liquid crystallinematerial to a light-scattering state. 7. The method as defined in claim6 wherein the liquid crystalline material is arranged between twoelectrodes at least one of which is substantially transparent. 8. Themethod of imaging a liquid crystalline material comprising,

providing a layer of a liquid crystalline material shaped in imageconfiguration between two electrodes at least one of which issubstantially transparent, said liquid crystalline material comprising acomposition of claim 1, and

applying an electric field across said liquid crystalline material, saidelectric field being of sufficient strength to transform said liquidcrystalline material to a light-scattering state whereby a visible imageis formed.

9. The method of imaging a liquid crystalline material comprising,

providing a layer of a liquid crystalline material between twoelectrodes at least one of which is substantially transparent and atleast one of which is shaped in image configuration, said liquidcrystalline material comprising a composition of claim 1, and

applying an electric field across said liquid crystalline material, saidelectric field being of sufficient strength to transform said liquidcrystalline material to a light-scattering state whereby a visible imageis formed.

10. The method of imaging a liquid crystalline material comprising,

providing a layer of a liquid crystalline material between twoelectrodes at least one of which is substantially transparent and atleast one of which includes a photoconductive surface, said liquidcrystalline material comprising a composition of claim energizing saidelectrodes by applying a potential thereto,

exposing said photoconductive surface to an imagewise pattern ofactivating electromagnetic radiation causing an imagewise electric fieldto be applied across said liquid crystalline material, said electricfield being of sufficient strength to transform said liquid crystallinematerial to a lightscattering state whereby a visible image is formed.

ill. The method of producing a display comprising providing a displaydevice comprising first and second spaced plates, at least one of whichis substantially transparent, a plurality of parallel electricallyconductive films on one face of said first plate, a plurality ofparallel electrically conductive films on one face of said second plate,the plurality of conductive films on at least one plate beingsubstantially transparent, said two plates being positioned with saidfaces bearing said parallel conductive films adjacent and parallel toeach other and the direction of said conductive films on one plate beingperpendicular to the direction of said conductive films on the otherplate, and a liquid crystalline material comprising a composition ofclaim 1 filling the space between said plates, and

selectively energizing at least one conductive film on each platecausing an electric field to be selectively applied across said liquidcrystalline material, said electric field being of sufficient strengthto selectively transform said liquid crystalline material to alight-scattering state.

2. Liquid crystalline compositions comprising from about 50 to about 70weight percent of
 3. Liquid crystalline compositions comprising fromabout 60 to about 80 weight percent of
 4. Liquid crystallinecompositions comprising from about 50 to about 80 weight percent of 5.Liquid crystalline compositions comprising from about 50 to about 70weight percent of
 6. A method for transforming a liquid crystallinematerial from the optically transparent state to a light-scatteringstate comprising, providing a liquid crystalline material comprising acomposition of claim 1, and applying an electric field across saidliquid crystalline material, said electric field being of sufficientstrength to transform said liquid crystalline material to alight-scattering state.
 7. The method as defined in claim 6 wherein theliquid crystalline material is arranged between two electrodes at leastone of which is substantially transparent.
 8. The method of imaging aliquid crystalline material comprising, providing a layer of a liquidcrystalline material shaped in image configuration between twoelectrodes at least one of which is substantially transparent, saidliquid crystalline material comprising a composition of claim 1, andapplying an electric field across said liquid crystalline material, saidelectric field being of sufficient strength to transform said liquidcrystalline material to a light-scattering state whereby a visible imageis formed.
 9. The method of imaging a liquid crystalline materialcomprising, providing a layer of a liquid crystalline material betweentwo electrodes at least one of which is substantially transparent and atleast one of which is shaped in image configuration, said liquidcrystalline material comprising a composition of claim 1, and applyingan electric field across said liquid crystalline material, said electricfield being of sufficient strength to transform said liquid crystallinematerial to a light-scattering state whereby a visible image is formed.10. The method of imaging a liquid crystalline material comprising,providing a layer of a liquid crystalline material between twoelectrodes at least one of which is substantially transparent and atleast one of which includes a photoconductive surface, said liquidcrystalline material comprising a composition of claim 1, energizingsaid electrodes by applying a potential thereto, exposing saidphotoconductive surface to an imagewise pattern of activatingelectromagnetic radiation causing an imagewise electric field to beapplied across said liquid crystalline material, said electric fieldbeing of sufficient strength to transform said liquid crystallinematerial to a light-scattering state whereby a visible image is formed.11. The method of producing a display comprising providing a displaydevice comprising first and second spaced plates, at least one of whichis substantially transparent, a plurality of parallel electricallyconductive films on one face of said first plate, a plurality ofparallel electrically conductive films on one face of said second plate,the plurality of conductive films on at least one plate beingsubstantially transparent, said two plates being positioned with saidfaces bearing said parallel conductive films adjacent and parallel toeach other and the direction of said conductive films on one plate beingperpendicular to the direction of said conductive films on the otherplate, and a liquid crystalline material comprising a composition ofclaim 1 filling the space between said plates, and selectivelyenergizing at least one conductive film on each plate causing anelectric field to be selectively applied across said liquid crystallinematerial, said electric field being of sufficient strength toselectively transform said liquid crystalline material to alight-scattering state.